If IP forwarding is enabled, then check your firewalls on Windows, the OpenVPN server, and the host on the 192.168.0.0/24 network. Make sure the Pi is set to allow forwards from the two networks in its firewall.

EDIT

Since this is a probable configuration issue, you will need to make sure the routes are announced.

Then create the directory, /etc/openvpn/server/ccd, and then create a file with the name of the common name of the certificate of the server. So if the server's certificate's common name is foo, then create the file /etc/openvpn/server/ccd/foo and put in the following:

IP forwarding has already been enabled. All other things you mentioned shouldn't be the problem because exchanging my old router with the current one, everything worked fine (some years ago I changed the routing table from old router but new router does not allow that). Could it be that the following is the problem: with new router the VPN Server's LAN is 192.168.0.0/24 and the local LAN from VPN client is 192.168.0.0/24 as well? With the old router the VPN Server's LAN was 192.168.1.0/24
– RufioFeb 6 at 21:42

I also assumed you configured OpenVPN correctly, did you push the routes with the server's configuration?
– markzzFeb 7 at 14:55

I added following lines: push "route 10.8.0.1 255.255.255.255" , push "route 10.8.0.0 255.255.255.0", push "route 0.0.0.0 " could the problem be that on both sides the local LAN has the same IP?
– RufioFeb 7 at 16:54

You should also have a line that has something along the lines of client-config-dir /etc/openvpn/server/ccd that in the specified directory is a couple of iroute lines.
– markzzFeb 7 at 17:23